Air conditioning with ice-brine slurry



A ril 26, 1966 J. w. MOHLMAN 3, 4

AIR CONDITIONING WITH ICE-BRINE SLURRY Filed Oct. 2, 1965 INVENTOR.

JOHN W. MOHLMAN ATTORNEY United States Patent M 3,247,678 AIR CONDITIONING WITH ICE-BRINE SLURRY John W. Mohlman, 4600 Van Alden St., Tarzana, Calif. Filed Oct. 2, 1963, Ser. No. 313,208 5 Claims. (Cl. 62-199) This invention relates generally to air conditioning by refrigeration and more particularly to refrigeration with an ice brine slurry.

Systems have been proposed heretofore for supplying cold water from a single refrigeration station as a common source to numerous ofl'lce, apartment and residential buildings for air conditioning purposes. The advantages of a common source for refrigeration, resulting in increased efliciency of operation, are evident; however, inasmuch as the heat capacity of Water as a refrigerant is relatively low, it is necessary to circulate relatively large volumes of water in a system in order to derive a required minimal of refrigeration. Large pipes and heavy duty equipment are needed.

' It is a general object of this invention to provide a system and method for air conditioning purposes utilizing an ice-brine slurry from a single refrigeration station for supplying numerous users with refrigeration, it being contemplated that such users (or customers) will pay for their metered consumption of refrigeration; By this invention the air to be cooled is passed in heat exchange relationship with the ice-brine slurry whereby the latent heat for melting of the ice is removed from the air. Thus, inasmuch as the heat of melting or heat of fusion for ice is about 80 times greater than the heat capacity of an equal weight of water, 'a relatively small Volume of icebrine slurry will provide the same amount of refrigeration as a much larger volume of cold water, with the result that smaller pipes and processing equipment are needed to convey the slurry from the refrigeration station to the air conditioning units.

The use of brine instead of Water makes it practicable to control the temperature at which ice crystals are formed for the slurry, thereby to effect control of the ice content in the slurry, as is explained more fully hereinafter.

\Further objects and advantages Will appear in the following part of this specification wherein the details of construction and mode of operation of a preferred embodiment of the invention are described with reference to the accompanying drawing, the single figure of which is a schematic representation of such embodiment.

In the drawing, the spaces -10, I l and '12, outlined by broken lines, represent a plurality of apartments or offices in a building to be furnished with metered refrigeration, or consider-ing this invention in a broader aspect, the spaces may be viewed as representing a plurality of buildings located in a section or district of suit-able area for distribution of refrigeration from a common refrigeration station. Each such apartment, office, or building has an air conditioning unit 14 each of which is represented in the drawing as comprising a coiled pipe :15 adjacent a fan 16 driven by a motor 417, the flow of icebrine slurry into the coiled pipe being controlled by a valve 18. The fan 17 circulates air within the space over and through the coil whereby the air is cooled with concomitant Warming of the slurry 'to an extent such that the ice in the slurry melts.

Each air conditioning unit is connected to a manifold conduit or flow line 20 leading from an elevated head tank 22. The head tank receives ice-brine slurry through a flow line 24- which includes a main pump as. An auxiliary pump 27 is connected at its outlet end to the flow line 24 by a branch line 28. The pumps receive icebrine slurry from a flow line 30 having inlet connections 31 and 32 for the pumps 26 and 627 respectively. The

3,247,678 Patented Apr. 26, 1966 auxiliary pump Q17 is designed for continuous operation whereas the larger pump 26 operates intermittently to meet the demand for refrigeration when the air conditioning units are in use. For controlling operation of the pump 26, the head tank 22 is equipped with a liquid level controller 34 which is electricallyconnected by a Wire 35 to the pump 26 such that when the ice-brine slurry in the head tank reaches a predetermined lower level, the pump '26 will be energized, and when the slurry reaches a predetermined upper level the pump 26 will be de-energized.

\Flow line 30 constitutes the product output line of a suitable refrigeration system for producing an ice brine slurry. For the illustrated embodiment the refrigeration system, designated generally by reference numeral 38, is of the type in which partial crystallization of water through freezing is effected by direct contact of the feed liquid with an immiscible and vol-atilizable refrigerant, as is described in US. Patent 3,098,733 for conversion of sea water to potable Water. The illustrated refrigeration system 38 comprises a freezer 40 containing brine 41. Fractional crystallization of the water in the brine occurs from the passing of an immisicible and volatilizable refrigerant, e.g., butane, in liquid phase in direct contact with the brine in the freezer, whereby the liquid refrigerant volatilizes in the freezer, deriving its heat of vaporization from the brine and thereby cooling the brine to a temperature at which ice crystals form in the brine.

A conduit 43 from the top of the freezer 40 and containing a compressor 45 conveys the refrigerant vapor from the freezer to a condenser 47 in which the compressed refrigerant vapors are converted to liquid phase. Reference numerals 48 and 49 design-ate an inlet and an outlet respectively for flow cooling of Water through the condenser. From the condenser the liquid refrigerant passes by line 51 to a reservoir 52. A pump 54 in flow line 56 pumps the liquid refrigerant from the reservoir to a sparger 58 in the freezer for direct contact with the brine in the freezer, thus completing the cycle of flow for the refrigerant.

-For controlling the operation of the compressor 45 and the liquid-refrigerant pump 54, there is an instrument 60 electrically connected by wire 61 to a temperature responsive element 62 positioned in the freezer proximate the slurry outlet 63 of the freezer. Instrument 60 is electrically connected by Wires 64 and 65 to the compressor 45 and the pump 54 respectively for on-otf control of the compressor and of the pump in response to reaching of predetermined temperature limits of the brine in the freezer as will appear more fully hereinafter.

The freezer 40 is replenished with feed brine through a return pipe or line or leading from the downstream end of the manifold pipe 20 to the brine inlet 69 of the freezer. Also connected to the brine return pipe 67 is another manifold flow line '70 to which the outlet end of each coiled pipe 15 of the air conditioning unit 14 is connected.

For efficient operation of a system of this invention, the system should be regulated to limit the ice content or the slurry which is passed from the refrigeration station 38 to the air conditioning units 14. Were the ice content of the slurry to reacha value greater than about 20 percent by weight, clogging of the equipment would be apt to occur. A slurry of an ice content less than about 10 percent would provide too thin a slurry for economical purposes. Then, too, the size of the ice crystals should be maintained below about 5 mm. in longest dimension to prevent clogging and to deter too rapid separation by floating of the ice crystals upon the brine liquor.

The factors of ice content and crystal size are regulated by controlled operation of the refrigeration station 38. When a brine of sodium chloride is used in the system of this invention, the salt content in the feed brine, is. brine entering the freezer at inlet 69, should preferably be from about 2 to about percent by weight. With sea water, for example, which has a salt content of about 3 /2 percent, ice crystals begin to form when the temperature of the brine reaches about 28.5 F., and an ice-brine slurry of about 20 percent ice will form by reducing the temperature of the brine by about two degrees lower than the initial freezing point. With a brine feed of about 2 percent salt content, reduction in temperature of about 1 F. from its initial freezing temperature of about 30 F. will produce a slurry of about 20 percent ice content. Thus it is that a higher salt content in the feed brine provides a greater range in freezing temperature for the production of a slurry of a given ice content, enabling more precise control of the ice content with the temperature controller 60.

The size of the ice crystals formed in the freezer is dependent upon the temperature of the volatilizing refrigerant and upon the residence time of the crystals in the freezer. The compressor 45 reduces the pressure in the freezer. When warm butane (about 85 to 90 F.) enters the freezer, it flashes to vapor because of the reduced pressure in the freezer and thereby substantially cools the liquid butane. For production of fine crystals the compressor should be powered to provide suificient vacuum in the freezer for reduction in the temperature of the flashing butane to from about 2 to 3 F. below the freezing temperature of the brine. The compressor 45 heats the butane vapor to a temperature in the neighborhood of about 100 F. Assuming the temperature of the cooling water for the condenser 47 to be from about 65 to 70 F., the temperature of the condensed butane from the condenser will be from about 85 to about 90 F.

The auxiliary pump 27 maintains continuous fiow of slurry through the system thereby providing for agitation of the slurry in the head tank 22 and for movement of brine through the freezer.

It will be understood that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of this disclosure, which do not constitute departures from the spirit and scope of the invention.

Having described the invention, what is claimed is:

1. A system for refrigeration of air in a space comprising freezer means admitting feed brine and exhausting an ice brine slurry, means to form ice crystals in the brine in the freezer, an elevated head tank, a first conduit and first pump for passing said slurry from the freezer to said head tank, a conduit in said space connected to said head tank for receiving said slurry from said tank, means for moving said air in heat exchange with said slurry in said space thereby to melt the ice in said slurry and to refrigerate said air, and means for returning the brine from, sa d eat c a g me to aid freezer.

2. A system forrefrigeration of air in space comprising a freezer means admitting feed brine and exhausting an ice-brine slurry, means for passing an immiscible and volatilizable refrigerant through the contents of the freezer thereby to form ice crystals in the brine in the freezer, an elevated head tank, a first conduit and first pump for passing said slurry from the freezer to said head tank, a conduit in said space connected to said head tank for receiving said slurry from said tank, means for moving said air in heat exchange with said slurry in said space thereby to melt the ice in said slurry and to refrigerate said air, and means for returning the brine from said heat exchange means to said freezer.

3. A system according to claim 2 and including an auxiliary pump and branch line connected to the outlet of said freezer and to said first conduit at a point downstream of said first pump for continuous flow from the freezer to said head tank thence to said space and return to said freezer.

4. A system according to claim 3 and including a liquid level controller on said head tank and operatively connected to said first pump for on-off control of said first pump in response to changes in the level of slurry between predetermined levels in the head tank.

5. A system for selective refrigeration of air in a plurality of spaces comprising a refrigeration station for converting a feed brine to an ice-brine slurry of from about 10 to 20 weight percent of ice crystals in residual brine, an elevated head tank, a first conduit and pump for passing said slurry from said station to said head tank, heat exchange air conditioning units in said spaces respectively, means for flowing said slurry from said head tank to said units, each of said air conditioning units comprising a fan and a conduit for passing air in heat exchange with said slurry thereby to melt the ice crystals in said slurry to reform said feed brine and to refrigerate said air, and means for returning said feed brine from said units to said station.

References Cited by the Examiner UNITED STATES PATENTS 310,025 12/1884 Brewer 62121 485,217 11/1892 Parshall 62114 X 1,185,597 5/1916 Eddy 62-442 X 2,101,953 12/1937 Oman 62--58 2,191,623 2/1940 Philipp 62-393 X 2,251,706 8/1941 Lowry 62331 2,349,671 5/1944 Newton 62333 X 2,751,762 6/1956 Colton 62-114 X 2,927,101 3/1960 Tegge et al 62--389 2,975,609 3/1961 Allander et al 62 4 4 2 x MEYER PERLIN, Primary Examiner.

ROBERT A. OLEARY, Examiner.

LLOYD L, KING, Assistant Examiner, 

1. SYSTEM FOR REFRIGERATION OF AIR IN A SPACE COMPRISING FREEZER MEANS ADMITTING FEED BRINE AND EXHAUSTING AN ICE BRINE SLURRY, MEANS TO FORM ICE CRYSTALS IN THE BRINE IN THE FREEZER, AN ELEVATED HEAD TANK, A FIRST CONDUIT AND FIRST PUMP FOR PASSING SAID SLURRY FROM THE FREEZER TO SAID HEAD TANK, A CONDUIT IN SAID SPACE CONNECTED TO SAID HEAD TANK FRO RECEIVING SAID SLURRY FROM SAID TANK, MEANS FOR MOVING SAID AIR IN HEAT EXCHANGE WITH SAID SLURRY IN SAID SPACE THEREBY TO MELT THE ICE IN SAID SLURRY AND TO REFRIGERATE SAID AIR, AND MEANS FOR RETURNING THE BRINE FROM SAID HEAT EXCHANGE MEANS TO SAID FREEZER. 